U.S. patent application number 13/442379 was filed with the patent office on 2012-09-13 for linear rod pump apparatus and method.
Invention is credited to Benjamin J. Gregory, Ronald G. Peterson.
Application Number | 20120230841 13/442379 |
Document ID | / |
Family ID | 46795745 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120230841 |
Kind Code |
A1 |
Gregory; Benjamin J. ; et
al. |
September 13, 2012 |
Linear Rod Pump Apparatus and Method
Abstract
An apparatus and method for pumping fluids, such as water and/or
hydrocarbons, from a subterranean formation or reservoir, include a
linear rod pump having a mechanical rack and pinion drive
arrangement, adapted for attachment to a pumping mechanism, such as
the polished rod at the top of a rod string in a hydrocarbon well.
The rack gear, of the rack and pinion drive arrangement, is adapted
for connection to a cable and pulley arrangement for imparting
motion to the polished rod. The pinion gear does not translate with
the rack gear, and is driven by a reversible motor for affecting up
and down reciprocating motion of the rack gear and pumping
mechanism. Some forms of the invention include a compressible gas
counter-balance arrangement. Some forms of the invention include an
electronic drive configured for dealing with electric power
generated by the motor during a portion of the pumping cycle.
Inventors: |
Gregory; Benjamin J.;
(Racine, WI) ; Peterson; Ronald G.; (Racine,
WI) |
Family ID: |
46795745 |
Appl. No.: |
13/442379 |
Filed: |
April 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11761484 |
Jun 12, 2007 |
8152492 |
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13442379 |
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60812795 |
Jun 12, 2006 |
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Current U.S.
Class: |
417/44.1 ;
417/415 |
Current CPC
Class: |
F04B 47/02 20130101;
F04B 47/04 20130101 |
Class at
Publication: |
417/44.1 ;
417/415 |
International
Class: |
F04B 17/03 20060101
F04B017/03; F04B 49/06 20060101 F04B049/06 |
Claims
1. A linear rod pumping apparatus, for imparting reciprocating
substantially vertical motion to a rod of a sucker-rod pump having
a pump stroke, the apparatus comprising: a linear mechanical
actuator arrangement, having a substantially vertically movable
member attached to the rod of the sucker-rod pump for imparting and
controlling vertical motion of the rod of the sucker-rod pump; and
a reversible motor having a reversibly rotatable element thereof
operatively connected to the substantially vertically movable
member of the linear mechanical actuator arrangement in a manner
establishing a fixed relationship between the rotational position
of the motor and the vertical movement of the vertically movable
member.
2. The apparatus of claim 1, wherein, the linear mechanical
actuator arrangement comprises: a rack and pinion gearing
arrangement, with the rack being disposed for operation in a
substantially vertical direction for reciprocating motion; the rack
being operatively connected in gear mesh relationship with the
pinion, and the pinion being operatively connected to the rotating
output of the motor, such that rotation of the motor in a first
direction is accompanied by a substantially vertically upward
motion of the rack, and such that a substantially vertically
downward motion of the rack is accompanied by rotation of the motor
rotatable element in a second direction opposite the first
direction; the rack also being operatively connected to the rod of
the sucker-rod pump for imparting vertically upward motion to the
rod of the sucker-rod pump along the pumping axis when the rack is
moving downward; and the rack further being operatively connected
to the rod of the sucker-rod pump such that the rod of the
sucker-rod pump exerts a substantially vertically upward directed
force on the rack, during a portion of the pump stroke.
3. The apparatus of claim 2, comprising: a pulley; and a cable
which is operatively connected to both the rack and the rod of the
sucker-rod pump, wherein the cable passes over the pulley.
4. The apparatus of claim 3, further comprising, one or more guide
rollers bearing against the rack, substantially opposite the
pinion, for urging the rack into gear mesh relationship with the
pinion.
5. The apparatus of claim 4, further comprising, a pair of guide
bars bearing against the rack, substantially opposite from one
another, for urging the rack into axial gear mesh relationship with
the pinion.
6. The apparatus of claim 2, further comprising, a control
arrangement operatively connected to the motor, for controlling the
motor.
7. The apparatus of claim 6, wherein: the control arrangement
operates the motor in a driving mode to urge downward movement of
the rack on an upward portion of the stroke of the pump rod; and
the control arrangement operates the motor in a braking mode during
upward movement of the rack on a downward portion of the stroke of
the pump rod.
8. The apparatus of claim 7, wherein, the control arrangement
includes an energy storage element for storing energy generated
during the braking mode of operation of the motor.
9. The apparatus of claim 8, wherein, the control arrangement is
configured for utilizing the stored energy in the energy storage
element to assist in driving the motor during the driving mode.
10. The apparatus of claim 9, wherein, the control arrangement also
includes an energy dissipation element for dissipating energy
generated during the braking mode of operation of the motor, and
the control arrangement is selectively configurable for operation
of one or the other of the energy storage and energy dissipation
elements.
11. The apparatus of claim 1, wherein, the linear mechanical
actuator arrangement comprises: a rack and pinion gearing
arrangement, with the rack being disposed for operation in a
substantially vertical direction for reciprocating motion; the rack
being operatively connected in gear mesh relationship with the
pinion, and the pinion being operatively connected to the rotating
output of the motor, such that rotation of the motor in a first
direction is accompanied by a substantially vertically upward
motion of the rack, and such that a substantially vertically
downward motion of the rack is accompanied by rotation of the motor
rotatable element in a second direction opposite the first
direction; the rack also being operatively connected to the rod of
the sucker-rod pump for imparting vertically upward motion to the
rod of the sucker-rod pump along the pumping axis when the rack is
moving upward; and the rack further being operatively connected to
the rod of the sucker-rod pump such that the rod of the sucker-rod
pump exerts a substantially vertically downward directed force on
the rack, during a portion of the pump stroke.
12. The apparatus of claim 11, comprising: a pulley attached to the
rack; and a cable which is operatively connected to both a fixed
point of the apparatus and the rod of the sucker-rod pump, wherein
the cable passes over the pulley, wherein movement of any distance
of the rack results in a movement of twice the distance by the
rod.
13. The apparatus of claim 12, further comprising, one or more
guide rollers bearing against the rack, substantially opposite the
pinion, for urging the rack into gear mesh relationship with the
pinion.
14. The apparatus of claim 13, further comprising, a pair of guide
bars bearing against the rack, substantially opposite from one
another, for urging the rack into axial gear mesh relationship with
the pinion.
15. The apparatus of claim 11, further comprising, a control
arrangement operatively connected to the motor, for controlling the
motor.
16. The apparatus of claim 15, wherein: the control arrangement
operates the motor in a driving mode to urge upward movement of the
rack on an upward portion of the stroke of the pump rod; and the
control arrangement operates the motor in a braking mode during
downward movement of the rack on a downward portion of the stroke
of the pump rod.
17. The apparatus of claim 16, wherein, the control arrangement
includes an energy storage element for storing energy generated
during the braking mode of operation of the motor.
18. The apparatus of claim 17, wherein, the control arrangement is
configured for utilizing the stored energy in the energy storage
element to assist in driving the motor during the driving mode.
19. The apparatus of claim 18, wherein, the control arrangement
also includes an energy dissipation element for dissipating energy
generated during the braking mode of operation of the motor, and
the control arrangement is selectively configurable for operation
of one or the other of the energy storage and energy dissipation
elements.
20. A linear rod pumping apparatus, for imparting reciprocating
substantially vertical motion to a rod of a sucker-rod pump having
a pump stroke, the apparatus comprising: a linear mechanical
actuator arrangement, having a substantially vertically movable
member attached to the rod of the sucker-rod pump for imparting and
controlling vertical motion of the rod of the sucker-rod pump with
the linear mechanical actuator arrangement comprising: a rack and
pinion gearing arrangement, with the rack being disposed for
operation in a substantially vertical direction for reciprocating
motion; the rack being operatively connected in gear mesh
relationship with the pinion, and the pinion being operatively
connected to the rotating output of the motor, such that rotation
of the motor in a first direction is accompanied by a substantially
vertically upward motion of the rack, and such that a substantially
vertically downward motion of the rack is accompanied by rotation
of the motor rotatable element in a second direction opposite the
first direction; the rack also being operatively connected to the
rod of the sucker-rod pump for imparting vertically upward motion
to the rod of the sucker-rod pump along the pumping axis when the
rack is moving downward; and the rack further being operatively
connected to the rod of the sucker-rod pump such that the rod of
the sucker-rod pump exerts a substantially vertically upward
directed force on the rack, during a portion of the pump stroke. a
pulley operatively associated with the linear mechanical actuator;
a cable which is operatively connected to both the rack and the rod
of the sucker-rod pump, wherein the cable passes over the pulley;
and a reversible motor having a reversibly rotatable element
thereof operatively connected to the substantially vertically
movable member of the linear mechanical actuator arrangement in a
manner establishing a fixed relationship between the rotational
position of the motor and the vertical movement of the vertically
movable member.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application is a Continuation-In-Part of U.S.
patent application Ser. No. 11/761,484, filed Jun. 12, 2007, now
U.S. Pat. No. ______, issued on Apr. ______, 2012, and claims the
benefit of U.S. Provisional Patent Application No. 60/812,795,
filed Jun. 12, 2006, the disclosure and teachings of both
application are incorporated herein in their entireties, by this
reference.
FIELD OF THE INVENTION
[0002] This invention relates to pumping of fluids, such as water
and/or hydrocarbons, from subterranean formations or reservoirs,
and more particularly to a pumping apparatus and method for use in
such pumping applications.
BACKGROUND OF THE INVENTION
[0003] For many years, the familiar "horse head", walking beam-type
mechanism has been used for pumping fluids such as water and/or oil
from subterranean formations. An example of such a walking beam
apparatus 50, connected to a polished rod 52 extending from a well
head 54 of a well 56, is illustrated as prior art in the attached
FIG. 1.
[0004] Conventional walking beam apparatuses have a number of
disadvantages, not the least of which is their large size. In
addition, performance of the walking beam pump apparatus is largely
a function of the design and connection of a number of mechanical
parts, which include massive counter-weights and complex drive
mechanisms which are difficult to control for obtaining maximum
pumping efficiency or to compensate for changes in condition of the
well over time.
[0005] As shown in FIG. 1, because of their large size and weight,
walking beam-type pumping mechanisms must typically be mounted on a
heavy concrete foundation 58, which may be poured in place or
pre-cast, located adjacent the well head 54. Construction of a
walking beam pumping mechanism, together with its foundation,
typically involves the efforts of several construction workers,
over a period which may be a week or more, to prepare the site, lay
the foundation 58, and allow time for the foundation 58 to cure, in
addition to the time required for assembling the various components
of the walking beam mechanism 50 onto the foundation 58 and
operatively connecting the mechanism to the polished rod 52. In
general, because of the costs of transporting the apparatus and the
concrete or pre-cast foundation to what may be a remote site and
the complexity of the site preparation and assembly process,
walking beam-type pumping mechanisms are generally only utilized in
long-term pumping installations.
[0006] The large size and massive weight of the walking beam
pumping mechanism and its foundation are also problematic when the
well 56 is decommissioned. Economic and contractual obligations may
require complete removal of the walking beam mechanism and its
foundation. It is desirable, therefore, to provide an improved
apparatus and method for operating the well 56, which eliminates,
or at least greatly reduces, the significant expenditures in time,
manpower, and money required to install and remove a pumping
apparatus used for extracting fluid from the well 56.
[0007] Another disadvantage of walking beam-type pumping
apparatuses is that they cannot typically operate at pumping speeds
much below 5 strokes per minute. As a result, it has been necessary
in the past, to only pump intermittently or to decommission wells
which could not sustain pumping at rates of at least 5 strokes per
minute, even though such wells would be capable of continued
operation at lower pumping speeds. Intermittent pumping creates
problems caused by varying levels of fluid in the well casing and
tubing and collection of contaminants into the pump during "off"
periods. As mentioned above, decommissioning a well equipped for
pumping with a walking beam-type mechanism is an arduous and costly
task. Further, government regulations frequently require the costly
process of sealing the well 56 with cement or other sealing means
when a well is decommissioned. It would be desirable, therefore, to
provide an improved apparatus and method, for pumping fluid from
the well 56, which could operate at considerably slower pumping
rates than a walking beam-type mechanism, in a form that could be
connected to the polished rod 52 in place of a walking beam
mechanism 50, at an existing well 56, to thereby extend the useful
life of the well 56 by operation at a pumping speed lower than
could otherwise be accomplished by the walking beam-type apparatus.
If such an improved pumping apparatus and method were available in
a form that could be quickly and simply installed on an existing
well 56, the necessity for, and cost related to, decommissioning
the well, and in particular the cost related to sealing the well
and removal of the walking beam mechanism and its foundation could
be deferred, perhaps indefinitely, while the well 56 is operated at
a low pumping rate.
[0008] Because of their large size and complexity, walking
beam-type pumping mechanisms typically need to be shut-down and
repaired on site. Although there have been attempts in the past to
develop portable walking beam apparatuses, such as those described
in U.S. Pat. No. 4,788,873, to Laney, such portable walking beam
pumping apparatuses have not gained widespread acceptance in the
art. It would be desirable, therefore, to have an improved pumping
apparatus and method, in which the pumping apparatus could be
readily transported to a well, and quickly installed in place of an
existing walking beam apparatus, or another one of the improved
pumping apparatuses previously attached to the well, to thereby
substantially reduce downtime of the well during the process of
performing maintenance and/or repairs of the pumping apparatus. It
would also be desirable for such an improved pumping apparatus and
method to allow for convenient installation and/or removal of the
improved pumping apparatus, substantially in a completely assembled
form, which could be initially assembled, or repaired, offline, at
a location remote from the well, while the well was continuing to
operate with another of the improved pumping apparatuses.
[0009] Another problem inherent in the use of walking beam-type
pumping apparatuses is that the apparatus must typically extend a
substantial distance above ground level in order to achieve a
desired pumping stroke length on the order of 3 to 6 feet. At such
substantial heights it may be difficult, if not impossible, to
operate irrigation equipment, for example, in close proximity to
the walking beam pumping apparatus, where such irrigation equipment
must pass over the top of the walking beam apparatus. U.S. Pat. No.
6,015,271, to Boyer et al. discloses a stowable walking beam
pumping unit having a foldable support structure to allow storage
of the pumping unit in a low profile position. A stowable walking
beam pumping unit, as disclosed by Boyer, has not been shown to be
commercially viable, however. It is desirable, therefore, for an
improved pumping apparatus and method to be operable in a form
having a low enough profile that other equipment, such as
irrigation pipes mounted on rolling supports can safely pass above
the pumping apparatus.
[0010] U.S. Pat. No. 4,114,375, to Saruwatari discloses replacing
the conventional walking beam pumping apparatus with a pump jack
device including a double acting piston and cylinder motor, with
the piston rod of the motor being adapted to be connected to the
polished rod projecting upwardly from a well head. A variable
displacement hydraulic pump, driven by a motor or engine, is
included in a closed hydraulic loop wherein conduits are connected
to a pair of output ports of the pump. A pump control means
controls the direction and volume of flow in the loop so as to
establish the stroke of the piston rod. A compressible fluid
counter-balance is provided for accumulation of energy during a
down stroke of the piston rod so that the energy may be returned to
the piston during the upstroke. The counter-balance cylinder may be
mounted coaxially above the motor and an additional closed chamber
may be provided in fluid communication with a charged chamber of
the counter-balance.
[0011] To date, the apparatus of Saruwatari has not achieved
commercial success.
[0012] Regardless of the type of pumping apparatus utilized,
controlling and optimizing the performance of a sucker-rod pumping
apparatus involves inherent difficulties. One factor which must be
taken into account is the stretching of the rod string, which
occurs during the upward portion of each pump stroke, and the
corresponding contraction of the rod string which occurs during the
downward portion of each pump stroke. The rod string, which may be
1000 feet or more long, acts much like an extension spring, which
is stretched during the portion of the pump stroke in which the rod
string is drawing the fluid upward within the well, and which then
contracts back to an essentially un-stretched state as the rod
string moves downward during a return portion of the pump stroke.
As a result of the rod stretch, an above-ground upward stroke of 32
inches, for a well approximately 1300 feet deep, may only result in
a down-hole stroke in the range of 24 to 26 inches, for example.
The difference between the magnitude and direction of movement of
the polished rod at the top of the well and the corresponding
reaction of the rod string and down-hole stroke of the pump
involves other complicating factors, including inherent damping
within the rod string, fluid damping which occurs during the pump
stroke and longitudinal vibrations and natural frequencies of the
rod string.
[0013] An additional difficulty occurs where the fluid being pumped
upward from the well contains a significant amount of entrained
gas. In such circumstances, a suction effect during the upward
stroke of the rod string causes the entrained gas to bubble out of
the fluid and form a foamy segment at the top of the column of
fluid being pulled upward toward the surface through action of the
down-hole components of the sucker-rod pump. Specifically, a
typical down-hole pump portion of a sucker-rod pump, apparatus is
located at the bottom of a length of tubing terminating in a fluid
outlet above the surface of the ground and includes a standing
valve, located at the lower end of the down-hole pump, and a
traveling valve, which is attached to the bottom end of the rod
string and is movable by the rod string within the down-hole pump
above the standing valve. The standing valve performs a check-valve
function which allows fluid to flow into the lower end of the
down-hole pump when the pressure within the down-hole pump is lower
than the pressure in the well casing outside of the down-hole pump.
When pressure within the down-hole pump is equal to, or greater
than, the pressure outside of the down-hole pump, the check-valve
function of the standing valve closes to preclude movement of fluid
out of the down-hole pump through the standing valve. The traveling
valve also includes a check-valve function, which works
substantially oppositely to the check-valve function of the
standing valve. When the pressure within the down-hole pump below
the traveling valve is lower than the pressure within the tubing
above the traveling valve, the traveling valve is closed.
Conversely, when the pressure within the down-hole pump below the
traveling valve is greater than the pressure within the tubing
above the traveling valve, the traveling valve opens and allows
fluid movement through the traveling valve, so that the traveling
valve can descend through the fluid in the down-hole pump.
[0014] By virtue of this arrangement, as the rod string pulls the
traveling valve upward, during the upward portion of the pump
stroke, the traveling valve is closed, and the upward motion of the
traveling valve within the tubing generates a suction in the
down-hole pump below the traveling valve which causes the standing
valve to open and allow fluid to be drawn upward into the portion
of the down-hole pump between the standing and traveling valves.
Where the sucker-rod pump is pumping a fluid with no entrained gas,
as soon as the rod string begins the downward portion of its
stroke, the standing valve closes and the stationary valve opens,
to thereby trap fluid within the down-hole pump above the standing
valve, and allow the traveling valve to move downward through the
trapped fluid within the down-hole pump, toward the standing valve,
to the bottom of the pump stroke, where the rod string reverses
direction and begins to pull the traveling valve upward at the
start of the next pump stroke.
[0015] For the above-mentioned exemplary well, pumping water for
dewatering coal bed methane and having a depth of approximately
1300 feet, the fluid load being moved upward by each stroke of the
pump once the entire length of tubing has been filled, for example,
would be 5400 pounds, and the weight of the rod string would be
approximately 1800 pounds. As a result, during each stroke of the
pump, the load on the rod string varies approximately by the 5400
pound fluid load, which causes a significant change in the length
of the rod string, as the rod string stretches and contracts during
each pump stroke. Fluid damping effects which occur as a result of
the movement of the traveling valve upward and downward through
fluid within the tubing and viscous effects related to the flow of
the fluid upward within the tubing also affect the dynamic
performance of the rod string.
[0016] Other complications also occur in wells having a fluid in
the form of a liquid having entrained gas. In these wells, the
traveling valve does not open immediately as it begins the downward
portion of its movement within the down-hole pump, due to the
presence of the foamy portion of the fluid column existing between
the traveling valve and the liquid portion of the fluid column. The
traveling valve must travel downward in the down-hole pump some
distance while compressing the gas which has foamed out of the
fluid before the suction effect dissipates to the point where the
pressure difference across the traveling valve is such that the
traveling valve can open.
[0017] As will be readily understood by those having skill in the
art, accurately predicting the down-hole performance of the
sucker-rod pump for a given input at the polished rod above the
surface of the ground is a challenging design problem, with the
specific difficulties discussed briefly above being far from
totally inclusive.
[0018] The problems of effectively and efficiently operating a
sucker-rod pump apparatus are addressed in significantly greater
detail in a commonly assigned U.S. Pat. No. 7,168,924 B2, to Beck
et al., titled "Rod Pump Control System Including Parameter
Estimator." The Beck et al. patent also discloses a rod pump
control system, which includes a parameter estimator that
determines, from motor data, parameters relating to operation of
the rod pump and/or generating a down-hole dynamometer card,
without the need for external instrumentation such as down-hole
sensors, rod load sensors, flow sensors, acoustic fluid level
sensors, etc. In some embodiments disclosed by Beck et al., having
a pumping apparatus driven by an electric motor, instantaneous
current and voltage, together with pump parameters estimated
through the use of a computer model of the sucker-rod pump, are
used in determining rod position and load. The rod position and
load are used to control the operation of the rod pump to optimize
operation of the pump. Beck et al. also discloses a pump-stroke
amplifier that is capable of increasing pump stroke without
changing the overall pumping speed, or in the alternative,
maintaining the well output with decreased overall pumping
speed.
[0019] The commonly assigned Beck et al. patent, also provides a
detailed description of the considerable additional complexity
involved in operating a sucker-rod pump with a walking beam pumping
apparatus, or with prior belt driven pumping units, and further
provides a method and apparatus for efficiently and effectively
controlling a sucker-rod pumping apparatus having a rod string
driven by a walking beam pumping apparatus, or other types of
previously-known pumping apparatuses.
[0020] With regard to the present invention, the detailed
descriptions within Beck et al., of the manner in which the
inherent difficulties of operating a sucker-rod pump apparatus are
compounded by a complex pumping apparatus such as the typical
walking-beam-type apparatus serve as ample evidence of the
desirability of providing a new and improved pumping apparatus for
use with a sucker-rod pump, which is not subject to the multitude
of complexities involved in controlling prior pumping apparatuses
such as the typical walking-beam-type pumping apparatus.
[0021] Even though the performance of walking-beam pump and other
types of prior pumping apparatuses can be substantially improved
through practicing the teachings of Beck et al., it is, therefore,
still highly desirable to provide an improved apparatus and method
for use in pumping fluids such as water and/or hydrocarbons from
subterranean formations and reservoirs in a form overcoming
problems such as, and in addition to, those discussed above. It is
further desirable that such improvements be provided in a form
which is considerably smaller in physical size than conventional
walking beam apparatuses and also in a form which is less complex
and more readily controllable and/or adjustable than prior
conventional walking beam-type apparatuses. It is further desirable
that such an improved apparatus and method provide advancements
over the pump jack device of Saruwatari, in a form that is
commercially viable.
BRIEF SUMMARY OF THE INVENTION
[0022] The invention provides an improved apparatus and method for
pumping fluids, such as water and/or hydrocarbons, from a
subterranean formation or reservoir, through use of a linear rod
pumping apparatus having a linear mechanical actuator arrangement
and a reversible motor operatively connected for imparting
reciprocating, substantially vertical motion to a rod string of a
sucker-rod pump. The linear mechanical actuator arrangement has a
substantially vertically movable member attached to the polished
rod of the sucker-rod pump for imparting and controlling vertical
motion of the rod string of the sucker-rod pump. The reversible
motor has a reversibly rotatable element thereof operatively
connected to the substantially vertically movable member of the
linear mechanical actuator arrangement in a manner establishing a
fixed relationship between the rotational position of the motor and
the linear position of the vertically movable member.
[0023] Apparatus and methods, in accordance with the present
invention, have demonstrated their commercial viability, and the
considerable advantages that can be obtained through practice of
the invention, during operational field testing on actual
hydrocarbon wells.
[0024] In some forms of the invention, a linear rod pumping
apparatus includes a mechanical rack and pinion drive arrangement
adapted for attachment to a pumping mechanism, such as the polished
rod at the top of a rod string in a hydrocarbon well. The rack gear
of the rack and pinion drive arrangement is adapted for connection
to, and translating movement with, the polished rod. The pinion
gear does not translate with the rack gear, and is driven by a
reversible motor for effecting up and down reciprocating motion of
the rack gear and pumping mechanism.
[0025] In some forms of the invention, a compressible gas cylinder
is utilized to provide a counter-balancing force which counteracts
generally downwardly directed forces which are inherently applied
to the reciprocating pumping mechanism by the rod string.
[0026] In other forms of the invention, a linear rod pump
apparatus, according to the invention, is utilized without a
pressurized gas counter-balance cylinder.
[0027] In some forms of the invention, the pinion gear is driven by
a reversible electric motor. The electric motor may be driven by an
electronic drive, having a configuration in accordance with the
invention, with the drive being controlled by a controller
configured according to the invention.
[0028] A drive and/or controller, according to the invention, may
provide energy storage and/or dynamic braking to accommodate energy
generation within the drive circuit, resulting from reversals in
direction of rotation of the drive motor and/or inherent cyclical
fluctuations on the electrical buses of the drive mechanism,
particularly during the downward stroke of the pump mechanism, when
gravitational force is essentially driving the motor as a
generator.
[0029] In various embodiments of the invention, energy generated
during the pumping process may be stored within a capacitor bank
section of the drive and used on a subsequent upstroke of the pump
for enhancing overall pumping efficiency of a linear rod pump
apparatus and/or method, according to the invention. Alternatively,
in some forms of the invention, the drive includes a regenerative
control section, which modulates energy generated during the
pumping cycle in such a manner that it can be transferred back to
the source of electrical power supplying power through the drive to
the motor. In yet other forms of the invention, the drive may
include a dynamic braking section, in which electrical energy
developed during the pumping process is dissipated across a dynamic
braking resistor, of the drive, according to the invention.
[0030] A given embodiment of a drive and controller, according to
the invention, may include any one or all of the aforementioned:
capacitor bank section; regenerative control section; and/or
dynamic braking section. In some forms of the invention, all three
sections will be provided within the drive, to allow for adaptation
of the drive for operation in various installations. Where it is
not desirable, or practical, to transfer power back to the source
of electrical power to the drive, such as might be the case in an
installation having an engine driven electrical generator, the
invention may utilize only one or both of the capacitor bank
section or dynamic brake section of the drive. Should circumstances
change, such as electrical power from a power grid becoming
available at the well site, so that the engine driven generator can
be eliminated, the drive can then be simply reconfigured to make
use of the regenerative control section.
[0031] A linear mechanical actuator arrangement, according to the
invention, may include a rack and pinion gearing arrangement, with
the rack being disposed for operation in a substantially vertical
direction, for reciprocating motion along a pumping axis. The rack
may be operatively connected in gear mesh relationship with the
pinion, and the pinion may be operatively connected to the rotating
output of the reversible motor, such that rotation of the motor in
a first direction is accompanied by a substantially vertically
upward motion of the rack along the pumping axis, and such that a
substantially vertically downward motion of the rack along the
pumping axis is accompanied by rotation of the motor rotatable
element in a second direction opposite the first direction. The
rack may also be operatively connected to the rod of the sucker-rod
pump for imparting vertically upward motion to the rod of the
sucker-rod pump along the pumping axis when the rack is moving
upward. The rack may be further operatively coupled to the rod of
the sucker-rod pump such that the rod exerts a substantially
vertically downward directed force on the rack while the rack is
moving downward, acting substantially along the pumping axis,
during a portion of the pump stroke.
[0032] The rack may also be operatively connected through one or
more cables to the rod of the sucker-rod pump for imparting
vertically upward motion to the rod of the sucker-rod pump along
the pumping axis when the rack is moving downward. The rack may be
further operatively coupled through one or more cables to the rod
of the sucker-rod pump such that the rod, acting substantially
along the pumping axis, exerts a substantially vertically upward
directed force on the rack during a portion of the pump stroke.
[0033] In some forms of the invention, the rack of a rack and
pinion gearing arrangement has a longitudinally directed opening
therein, extending along the pump axis from a bottom end of the
rack to the top end of the rack when the linear mechanical actuator
is operatively disposed above the sucker-rod pump. The rack may
further have an upper end thereof adapted for operative attachment
of the rod thereto.
[0034] The upper end of the rack may define a hole extending
therethrough, and an upper load bearing surface. The hole in the
upper end may be configured such that the upper end of the rod may
slideably extend through the hole. The linear mechanical actuator
arrangement may further include a rod securing clamp or collar
fixedly attached to the upper end of the rod above the upper end of
the rack. Such a rod securing clamp or collar may have a lower load
bearing surface thereof adapted for bearing contact with the upper
load bearing surface of the upper end of the rack for transferring
force between the rod and the upper end of the rack when the lower
load bearing surface of the collar is in contact with the upper
load bearing surface of the upper end of the rack.
[0035] In some forms of the invention, a rack, of a rack and pinion
gearing arrangement, may be configured to have a substantially
U-shaped cross-section, with first and second legs of the U
extending from a bight section thereof, in such a manner that the
legs and bight define a longitudinally extending opening in the
rack having the form of an open channel disposed about the pumping
axis, with an outer surface of the bight that faces substantially
oppositely from the legs including gear teeth of the rack,
configured for engagement with corresponding gear teeth of the
pinion.
[0036] A linear rod pumping apparatus, according to the invention,
may further include one or more guide rollers, disposed to bear
against the longitudinally extending distal edges of the legs of
the rack at a point or points substantially opposite the pinion,
for urging the rack into gear mesh relationship with the pinion. An
apparatus, according to the invention, may further include a pair
of guide bars bearing against the legs of the rack, substantially
opposite from one another, for urging the rack into axial gear mesh
relationship with the pinion.
[0037] An apparatus, according to the invention, may also include a
pinion housing having a longitudinally extending opening therein,
disposed about the pumping axis, for passage therethrough of the
rack, and defining a rotational axis of the pinion. The rotational
axis of the pinion may be laterally offset from, and extend
substantially perpendicularly to, the pumping axis. A first
anti-drive end of the pinion may be journaled in a pinion bearing
disposed in and mounted to the pinion housing. A second drive-end
of the pinion may be adapted for connection to an output element of
a drive mechanism such as a motor or gearbox, and for being
supported by an output bearing of the drive mechanism.
[0038] Some forms of an apparatus, according to the invention, may
include a gearbox operatively connected between the motor and the
linear mechanical actuator apparatus. The gearbox may have an input
element thereof operatively attached to the rotatable element of
the motor for rotation therewith. The gearbox may also have an
output element thereof operatively attached to the pinion for
rotation therewith. In some forms of the invention, the input and
output elements of the gearbox may be arranged substantially at a
right angle to one another, with the output element being oriented
for alignment with and rotation substantially about the pinion
axis, and with the input element of the gearbox and the rotatable
element of the motor being oriented substantially parallel to the
pumping axis.
[0039] Some forms of an apparatus, according to the invention, may
include one or more cables operatively connected to the upper end
of the rack and to the polished rod and one or more pulleys to
guide the one or more cables such that the motion of the rack
imparts motion to the polished rod substantially along the pumping
axis. The pulleys, in some configurations are in a fixed position
relative to the linear mechanical actuator and in some
configurations the pulleys are attached to the rack which imparts
reciprocating up and down movement of the pulleys.
[0040] Some forms of the invention also include a control
arrangement, operatively connected to the motor, for controlling
the motor. The control arrangement may operate the motor in a
driving mode to urge upward movement of the rack on a lifting
portion of the stroke of the pump rod. The control arrangement may
also operate the motor in a braking mode, during downward movement
of the rack, on a return/fill portion of the stroke of the pump
rod.
[0041] In some forms of the invention, the control arrangement may
include an energy storage element for storing energy generated
during the braking mode of operation of the motor. In other forms
of the invention, the control arrangement may be configured for
utilizing the stored energy in the energy storage element to assist
in driving the motor during the driving mode. In some forms of the
invention, the control arrangement may include an energy
dissipation element for dissipating energy generated during the
braking mode of operation of the motor. In some forms of the
invention, a control arrangement may be selectively configurable
for operation of one or the other of the energy storage and energy
dissipation modes. A control arrangement, according to the
invention, may further include sensing arrangements for sensing one
or more parameters of the group of parameters consisting of: linear
position of the rack along the pumping axis; rotational position of
the pinion about the pinion axis; motor torque; motor speed; motor
acceleration; and motor input power.
[0042] A control arrangement, according to the invention, may
include a pump rod dynamics model, for use in controlling operation
of the motor. In forms of the invention having a sensing
arrangement, the sensing arrangement may determine linear position
of the rack twice during each pump cycle, once on the upstroke and
once on the downstroke.
[0043] A control arrangement, according to the invention, may be
configured for detecting fault conditions and applying corrective
action to modify operation of the motor. Fault conditions which may
be detected, in accordance with the invention, may include, but are
not limited to: loss of power to the motor; invalid or missed
position reference; non-filling of the pump; and motor overheating.
Corrective actions may include, but are not be limited to, applying
braking force through the motor, or actuation of brake mechanisms
external to the linear rod pumping arrangement; changing stroke
length and/or frequency; dwelling for a period of time in an off
position; or operating the motor to slowly lower the rack to the
lower mechanical limit of travel.
[0044] The invention may be practiced with a variety of different
types of motors, including, electrical, hydraulic, and
pneumatic.
[0045] An apparatus, according to the invention, may also include a
pneumatic energy storage element operatively connected for storing
energy generated during downward movement of the vertically movable
element, and utilizing the stored energy for aiding upward vertical
movement of the vertically movable element. In forms of the
invention including a rack and pinion, the pneumatic energy storage
element may be operatively connected for storing energy generated
during the downward movement of the rod, and releasing the stored
energy for aiding upward movement of the rod.
[0046] In some forms of the invention, a spring member is
operatively positioned below the lower end of the rack and
configured for engaging and applying an upwardly directed force to
the lower end of the rack when the lower end of the rack has moved
beyond a normal lower position of the rack during a pump stroke. In
some forms of the invention, a spring member operatively positioned
below the lower end of the rack may be positioned and configured
for engaging and applying an upwardly directed force to the lower
end of the rack during a portion of each pump stroke.
[0047] In some forms of the invention, a spring member is
operatively attached to the lower end of the rack, and configured
for engaging and applying a downwardly directed force to the lower
end of the rack, when the lower end of the rack has moved beyond a
normal upper position of the rack during a pump stroke. In some
forms of the invention, a spring member operatively attached to the
lower end of the rack, may be positioned and configured for
engaging and applying a downwardly directed force to the lower end
of the rack during a portion of each pump stroke.
[0048] Some forms of the invention include an oil sump disposed
around the lower end of the rack and configured for containing a
volume of lubricant therein and for receiving a portion of the rack
adjacent the lower end of the rack to thereby apply the lubricant
to the rack. The sump and the volume of lubricant therein may be
configured and positioned such that the portion of the rack is
immersed into the lubricant during at least a portion of each
stroke of the pump. The sump may include an inner and outer
longitudinally extending, radially spaced tubular wall, sealingly
connected at lower ends thereof to define an annular-shaped cavity
therebetween, for receipt within the cavity of the volume of
lubricant, and terminating in an annular-shaped opening between the
upper ends of the inner and outer tubular walls. The inner tubular
wall of the sump may have, an inner periphery thereof disposed
about the pump rod, and an outer periphery thereof disposed within
the opening in the rack. The outer tubular wall of the sump may
have an inner periphery thereof disposed about the rack.
[0049] In an apparatus having a sump, according to the invention,
the apparatus may further include a spring member operatively
positioned within the cavity in the sump below the lower end of the
rack and configured for engaging and applying an upwardly directed
forced to the lower end of the rack when the lower end of the rack
has moved beyond a normal position of the rack during a pump
stroke. In some forms of the invention, such a spring member,
operatively positioned within the cavity of the sump below the
lower end of the rack, may be configured for engaging and applying
an upwardly directed force to the lower end of the rack during a
portion of each pump stroke.
[0050] Some forms of the invention include a position sensing
arrangement for sensing a position of the rack along the pump axis.
The position sensing arrangement may include a stationary position
sensor and a sensor flag. The stationary position sensor is
disposed adjacent the rack substantially at a mid-stroke position
along the pumping axis. The sensor flag is attached to the rack and
disposed such that the flag is juxtaposed with, and sensed by, the
sensor during each pumping stroke.
[0051] In some forms of sensing arrangements, according to the
invention, an upper sensor flag and a lower sensor flag are axially
spaced from one another along the rack, to form a gap between the
upper and lower flags, with the gap being substantially centrally
disposed along the rack. The upper sensor flag extends
substantially from the upper end of the rack to a lower edge of the
upper sensor flag defining an upper end of the gap between the
upper and lower sensor flags, and the lower sensor flag extends
substantially from the lower end of the rack to an upper edge of
the lower sensor flag defining the lower end of the gap between the
upper and lower sensor flags. With such an arrangement, the sensor
may produce an output having a substantially square-wave shape,
with a step change from a first state, whereat one or the other of
the flags is juxtaposed with the sensor, to a second state whereat
the gap is juxtaposed with the sensor.
[0052] The invention may also be practiced in the form of a method
for constructing, operating, maintaining, or replacing a linear rod
pumping apparatus according to the invention.
[0053] In one form of the invention, a method is provided for
operating a linear rod pumping apparatus including a linear
mechanical actuator arrangement and a reversible motor, where the
linear mechanical actuator has a substantially vertically movable
member adapted for attachment thereto of the rod of a sucker-rod
pump, for parting and controlling vertical motion of the rod of the
sucker-rod pump. The reversible motor has a reversibly rotatable
element thereof, operatively connected to the substantially
vertical member of the linear mechanical actuator arrangement in a
manner establishing a fixed relationship between the rotational
position of the rotatable element of the motor and the vertical
position of the vertically movable member, with the method
including, operating the motor in a manner imparting reciprocating
substantially vertical motion to the vertically movable member. The
method may further include determining dynamic operation of the
pump rod, and controlling the motor in accordance with the dynamic
operation of the pump rod.
[0054] A method, according to the invention, may include operating
the motor in a driving mode, for applying torque to the rotatable
element of the motor in a first direction to urge rotation of the
rotatable element in the first direction on an upward portion of a
stroke of the pump rod. A method, according to the invention, may
further include operating the motor in a braking mode, for applying
a net torque to the rotatable element in the first direction, for
resisting rotation of the rotatable element in the opposite
direction on a downward portion of the stroke of the pump rod.
[0055] In some forms of the invention, the motor generates energy
during the braking mode, and a method, according to the invention,
may further include extracting at least a portion of the generated
energy during the braking mode of operation. The extracted energy
may be utilized, in some forms of the invention, to assist in
driving the motor during at least one of the driving and braking
modes. Alternatively, the energy generated during the braking mode
of operation of the motor may be dissipated.
[0056] The invention may also include controlling the motor in
accordance with sensed values of one or more parameters selected
from the group of parameters consisting of, linear position of the
vertically movable member, rotational position of the rotatable
element of the motor, motor torque, motor speed, motor
acceleration, and motor input power. In some forms of the
invention, one or more of the sensed values of parameters used for
controlling the motor are sensed above-ground, rather than through
the use of down-hole sensors. In some forms of the invention, all
sensed values of the parameters used for controlling the motor are
sensed above-ground.
[0057] Some forms of the invention may include detecting a fault
condition, and taking corrective action. Some forms of the
invention may include detecting a fault condition from the group of
faults consisting of, loss of power to the motor, invalid or missed
position reference, loss of control of the motor, non-filling of
the pump, breakage and/or separation of the pump rod, and
overheating of the motor.
[0058] In some forms of the invention, the corrective action taken
may be one of a group of corrective actions from the group
consisting of, applying braking, changing pump stroke length,
changing pump stroke frequency, dwelling in a non-pumping state,
operating the motor to slowly lower the rack to the lower
mechanical limit of travel, and entering a start-up mode of
operation.
[0059] In some forms of the invention, where a linear rod pumping
apparatus, according to the invention, includes a position sensing
arrangement having a stationary position sensor disposed adjacent
the vertically movable member, approximately at a mid-stroke
position thereof along the pumping axis, and a sensor flag attached
to the vertically movable member and disposed such that the flag is
juxtaposed with, and sensed by, the sensor during each pumping
stroke, a method, according to the invention, may include detecting
the vertical position of the vertically movable member by detecting
juxtaposition of the flag with the sensor during each pump
stroke.
[0060] In some forms of the invention, a sensing arrangement
includes an upper sensor flag and a lower sensor flag, axially
spaced from one another along the rack, to form a gap between the
upper and lower flags, with the gap being substantially centrally
longitudinally disposed along the rack. The upper sensor flag may
extend substantially from the upper end of the rack to a lower edge
of the upper sensor flag, defining an upper end of the gap between
the upper and lower flags. In similar fashion, the lower sensor
flag may extend substantially from the lower end of the rack to an
upper edge of the lower sensor flag, to thereby define the lower
end of the gap between the upper and lower sensor flags. Where such
an arrangement is provided, a method, according to the invention,
may include detecting the vertical position of the vertically
movable member by detecting juxtaposition of the sensor with at
least one of the upper and lower sensor flags during each pump
stroke. A method may further include detecting an output of the
sensor having a substantially square-wave shape, with a step change
form a first state while one or the other of the lower flags is
juxtapose with the sensor, to a second state when the gap is
juxtapose with the sensor.
[0061] In one form of the invention, a method is provided for
extending the operating life of a hydrocarbon well where the well
has a walking beam apparatus operatively connected to the well for
imparting reciprocating substantially vertical motion to a rod of a
sucker-rod pump stroke. The method may include disconnecting the
rod from the walking beam apparatus, and operatively connecting the
rod to a linear rod pumping apparatus including a linear mechanical
actuator arrangement and a reversible motor, according to the
invention. The linear mechanical actuator arrangement may include a
substantially vertically movable member configured for attachment
to the rod of the sucker-rod pump for imparting and controlling
vertical motion of the rod of the sucker-rod pump. The motor may
include a reversibly rotatable element thereof, operatively
connected to the substantially vertically movable member of the
linear mechanical actuator arrangement in a manner establishing a
fixed relationship between the rotational position of the motor and
the linear position of the vertically movable member.
[0062] A method for extending the operating life of a hydrocarbon
well may further include mounting the linear rod pumping apparatus
directly on the well head of the well, to thereby preclude the need
for a separate mounting structure for the linear rod pumping
apparatus. In some forms of a method, according to the invention,
the walking beam apparatus is left in place adjacent the well. Some
forms of a method, according to the invention, may include removal
of the walking beam pump, while operating the well with the linear
rod pumping apparatus.
[0063] A method for operating a hydrocarbon well, in accordance
with the invention, may include the steps of: installing a first
linear rod pumping apparatus on a well head of the well; operating
the well for a period of time with the first linear rod pumping
apparatus; removing the first linear rod pumping apparatus from the
well head, substantially without disassembly of the first linear
rod pumping apparatus; and replacing the first linear rod pumping
apparatus with a second substantially assembled linear pumping rod
apparatus; and operating the well with the second linear rod
pumping apparatus. The method may further include disposing of the
first linear rod pumping rod apparatus. Alternatively, a method may
include repairing and/or refurbishing of the first linear rod
pumping apparatus offline, while the well is being operated with
the second linear pumping rod apparatus.
[0064] Other aspects, objects and advantages of the invention will
be apparent from the following detailed description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0065] FIG. 1, labeled as prior art, is a schematic illustration of
a typical walking-beam-type pumping mechanism, mounted on a
foundation located adjacent a well head of a hydrocarbon well, and
attached to pump fluid from the hydrocarbon well.
[0066] FIG. 2 is a schematic illustration of a first exemplary
embodiment of a linear rod pumping apparatus, according to the
invention, mounted on the well head of a hydrocarbon well.
[0067] FIG. 3 is a schematic illustration of a second exemplary
embodiment of a linear rod pumping apparatus, according to the
invention, mounted on the well head of the well shown in FIG. 1,
and operatively connected for pumping fluid from the well, instead
of the walking beam apparatus, with the linear rod pumping
apparatus and walking beam pumping apparatus being drawn to the
same scale, to illustrate the substantial reduction in size and
complexity of the linear rod pumping apparatus, according to the
invention, as compared to a walking beam apparatus which was
providing similar pumping output as the second exemplary embodiment
of the linear rod pumping apparatus, according to the
invention.
[0068] FIG. 4 is an external perspective view of the second
exemplary embodiment of the linear pumping apparatus, according to
the invention, shown in FIG. 3.
[0069] FIG. 5 is a partially cut-away perspective illustration of
the second exemplary embodiment of a linear pumping apparatus,
according to the invention, shown in FIG. 4.
[0070] FIG. 6 is an exterior orthographic illustration of the
second exemplary embodiment of the linear pumping apparatus,
according to the invention, shown in FIGS. 3-5.
[0071] FIG. 7 is a partial cross-sectional illustration of the
second exemplary embodiment of the linear rod pumping apparatus,
according to the invention, shown in FIG. 6.
[0072] FIG. 8 is a schematic cross-section view of the second
exemplary embodiment of the linear pumping apparatus, according to
the invention, shown in FIGS. 3-7.
[0073] FIG. 9 is an enlarged, partial cross-sectional, schematic
illustration of a variation of the second exemplary embodiment
having a tubular-shaped spacer disposed between a rod clamp and the
upper end of a rack of a rack and pinion arrangement of the second
exemplary embodiment of the invention.
[0074] FIG. 10 is a schematic cross-sectional illustration, taken
along line 10-10 in FIG. 8.
[0075] FIG. 11 is a graphical illustration of an exemplary
substantially square-wave output produced by a sensing mechanism,
according to the invention, of the second exemplary embodiment of
the linear rod pumping apparatus, according to the invention, as
shown in FIGS. 8 and 10.
[0076] FIG. 12 is a schematic cross-section of a third exemplary
embodiment of a linear rod pumping apparatus, according to the
invention.
[0077] FIG. 13 is a schematic cross-sectional illustration of a
fourth exemplary embodiment of a linear rod pumping apparatus,
according to the invention, which includes a pneumatic storage
apparatus and regulator, for supply a counter-balance force to
elements of the linear rod pumping apparatus.
[0078] FIG. 14 shows a first exemplary embodiment of a motor drive,
for use in a control arrangement in embodiments of the invention
having an electric motor.
[0079] FIG. 15 shows a second exemplary embodiment of a motor
drive, for use with an electric motor in practicing the
invention.
[0080] FIG. 16 is an exterior orthographic illustration of an
exemplary embodiment of the linear pumping apparatus, according to
the invention, wherein the rack is operatively connected to the
polished rod by a cable, with the cable passing over a pulley
located above the uppermost extension of the rack.
[0081] FIG. 17 is an exterior perspective illustration of the
exemplary embodiment of the linear pumping apparatus illustrated in
FIG. 16, according to the invention, wherein the rack is
operatively connected to the polished rod by a cable.
[0082] FIG. 18 is an exterior orthographic illustration of an
exemplary embodiment of the linear pumping apparatus, according to
the invention, wherein the rack is operatively connected to the
polished rod by a cable, such that the movement distance of the
polished rod is twice the movement distance of the rack, with the
cable passing over a pulley located above the rack and with the
pulley coupled to the rack to impart reciprocating up and down
movement of the pulley.
[0083] FIG. 19 is an exterior perspective illustration of the
exemplary embodiment of the linear pumping apparatus illustrated in
FIG. 18, according to the invention, wherein the rack is
operatively connected to the polished rod by a cable, such that the
movement distance of the polished rod is twice the movement
distance of the rack.
[0084] While the invention will be described in connection with
certain preferred embodiments, there is no intent to limit it to
those embodiments. On the contrary, the intent is to cover all
alternatives, modifications and equivalents as included within the
spirit and scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0085] FIG. 2 is a schematic illustration of a first exemplary
embodiment of a linear rod pumping apparatus 100 mounted on the
well head 54 of a hydrocarbon well 56. The well includes a casing
60 which extends downward into the ground through a subterranean
formation 62 to a depth sufficient to reach an oil reservoir 64.
The casing 60 includes a series of perforations 66, through which
fluid from the hydrocarbon reservoir enter into the casing 60, to
thereby provide a source of fluid for a down-hole pumping apparatus
68, installed at the bottom of a length of tubing 70 which
terminates in an fluid outlet 72 at a point above the surface 74 of
the ground. The casing 60 terminates in a gas outlet 76 above the
surface of the ground 74.
[0086] The down-hole pumping apparatus 68 includes a stationary
valve 78, and a traveling valve 80. The traveling valve 80 is
attached to a rod string 82 extending upward through the tubing 70
and exiting the well head 54 at the polished rod 52. Those having
skill in the art will recognize that the down-hole pumping
apparatus 68, in the exemplary embodiment of the invention, forms a
traditional sucker-rod pump arrangement for lifting fluid from the
bottom of the well 56 as the polished rod 52 imparts reciprocal
motion to rod string 82 and the rod string 82 in turn causes
reciprocal motion of the traveling valve 80 through a pump stroke
84. In a typical hydrocarbon well, the rod string 82 may be several
thousand feet long and the pump stroke 84 may be several feet
long.
[0087] As shown in FIG. 2, the first exemplary embodiment of a
linear rod pump apparatus 100, according to the invention, includes
a linear mechanical actuator arrangement 102, a reversible motor
104, and a control arrangement 106, with the control arrangement
106 including a controller 108 and a motor drive 110. In all forms
of the invention, the linear mechanical actuator arrangement 102
includes a substantially vertically movable member attached to the
polished rod 52 for imparting and controlling vertical motion of
the rod string 82 and the sucker-rod pump 68. The reversible motor
of a linear rod pump apparatus, according to the invention,
includes a reversibly rotatable element thereof, operatively
connected to the substantially vertically movable member of the
linear mechanical actuator arrangement 102 in a manner establishing
a fixed relationship between the rotational position of the motor
104 and the vertical position of the rack 206. As will be
understood, by those having skill in the art, having a fixed
relationship between the rotational position of the motor 104 and
the vertical position of the polished rod 52 provides a number of
significant advantages in the construction and operation of a
sucker-rod pump apparatus, according to the invention.
[0088] FIG. 3 shows a second exemplary embodiment of a linear rod
pumping apparatus 200, according to the invention, mounted on a
standoff 202 to the well head 54, and operatively connected for
driving the polished rod 52. In FIG. 3, the second exemplary
embodiment of the linear rod pumping apparatus 200 is illustrated
to scale, adjacent to the walking beam pumping apparatus 50, to
show the substantial reduction in size, weight, and complexity
afforded through practice of the invention, as compared to prior
approaches utilizing walking beam apparatuses 50.
[0089] It will be noted that an arrangement such as the one
illustrated in FIG. 3, in which a linear rod pumping apparatus 200
is mounted adjacent a walking beam apparatus 50, might actually be
observed in practicing the invention where the walking beam
apparatus 50 is disconnected from the polished rod 52 and replaced
by the linear rod pumping apparatus 200 to extend the life of the
well 56 by utilizing the linear rod pumping apparatus 200 to pump
at a slower rate than is possible through use of the walking beam
apparatus 50.
[0090] It will be appreciated by those having skill in the art,
that where a linear rod pumping apparatus 200 is used to replace a
walking beam apparatus, or a previously installed embodiment of a
linear rod pumping apparatus according to the invention, the
replacement linear rod pumping apparatus 200 can be installed in a
fully assembled form, or in a substantially fully assembled form,
with only a minimal number of components, such as the upper section
214 of a housing, for example, being installed after the linear rod
pumping apparatus 200 is installed on the well head 54. As will
also be understood from the following description and inspection of
the drawings, it may be desirable, in practicing the invention, to
ship an otherwise substantially fully assembled linear rod pumping
apparatus, according to the invention, with components such as the
upper housing section 214 not installed, to thereby reduce the
physical size of the linear rod pump 200 in a manner that is more
compact to facilitate shipping and handling. As will be further
understood, the compact size of a linear rod pumping apparatus
according to the invention allows the linear rod pumping apparatus
that is being replaced to be conveniently removed in a fully
assembled or a substantially fully assembled form.
[0091] As shown in FIGS. 3-8, the second exemplary embodiment of
the linear rod pumping apparatus 200, according to the invention,
includes a linear mechanical actuator arrangement 204 which, in
turn, includes a rack and pinion gearing arrangement having a rack
206 and a pinion 208 operatively connected through a gearbox 210 to
be driven by a reversible electric motor 212 in a manner described
in more detail below.
[0092] As shown schematically in FIG. 8, the linear mechanical
actuator arrangement 204 of the second exemplary embodiment of the
linear rod pumping apparatus 200 includes a rack and pinion gearing
arrangement 206, 208 with the rack 206 being disposed for operation
in a substantially vertical direction for reciprocating motion
within a three piece housing having an upper, middle and lower
section 214, 216, 218 along a substantially vertically oriented
pumping axis 220. The rack 206 is operatively connected in gear
mesh relationship with pinion 208 and the pinion 208 is operatively
connected to a rotating output shaft 222 of the motor 212 (see FIG.
7) such that rotation of the motor output shaft in a first
direction is accompanied by a substantially vertically upward
motion of the rack 206 along the pumping axis 220, and such that a
substantially vertically downward motion of the rack 206 along the
pumping axis 220 is accompanied by rotation of the motor output
shaft 222 in a second direction opposite the first direction. The
rack 206 is also operatively connected to the polished rod 52 of
the sucker-rod pump 68, such that the rack 206 cannot exert a
substantially vertically downward directed force on the polished
rod 52.
[0093] As shown in FIG. 9, which is a section view taken along line
9-9 in FIG. 8, the rack 206 of the exemplary embodiment 200 has a
substantially U-shaped cross-section, with first and second legs
224, 226 extending from a bight section 228 in such a manner that
the legs and bight 224, 226, 228 define a longitudinally extending
opening in the rack 206 in the form of an open channel 230 disposed
about the pumping axis 220. An outer surface 232 of the bight 228,
facing substantially oppositely from the legs 226, 228 of the rack
206, is configured to form gear teeth of the rack 206 for
engagement with corresponding gear teeth in the pinion 208.
[0094] The longitudinally directed channel 230 in the rack 206
extends along the pumping axis 220 from a bottom end 234 of the
rack 206 to a top end 236 of the rack 206, with the upper end 236
of the rack 206 being adapted for operative attachment thereto of
the polished rod 52. Specifically, as shown in FIG. 8, the upper
end 236 of the rack 206 includes a top plate 238 having a hole 240
extending therethrough and defining an upper load bearing surface
241 of the upper end 236 of the rack 206.
[0095] The linear mechanical actuator apparatus 204, of the second
exemplary embodiment of the linear rod pumping apparatus 200, also
includes an actuator rod 242, having a lower end 244 thereof
fixedly attached to the top end of the polished rod 52 by a
threaded joint or other appropriate type of coupling. The actuator
rod 242 extends upward from the lower end 244, through the channel
230 in the rack 206 and the hole 240 in the top plate 238 of the
rack 206, and terminates at and upper end 246 of the actuator rod
242 which is disposed above the bearing surface 241 on the upper
surface of the top plate 238 of the rack 236. A rod clamp 248 is
fixedly attached below the upper end 246 of the actuator rod 242
and above the upper end 236 of the rack 206. The clamp 248 has a
lower load bearing surface thereof adapted for bearing contact with
the upper load bearing surface 241 of the upper end 236 of the rack
206, for transferring force between the actuator rod 242 and the
upper end 236 of the rack 206 when the lower load bearing surface
of the clamp 248 is in contact with the upper load bearing surface
241 on the upper end 236 of the rack 206.
[0096] The clamp 248, of the exemplary embodiment 200 forms an
expanded upper end of the actuator rod 242 having a configuration
that is incapable of entry into or passage through the hole 240 in
the upper end 236 of the rack 206. It will be further appreciated
that, to facilitate installation of the linear rod pumping
apparatus 200 on the well head 54, the actuator rod 242 may be
allowed to extend some distance beyond the collar 248, to thereby
provide some measure of adjustment to accommodate variations in the
positioning of the upper end of the polished rod 52, with respect
to the lower end of the lower section 218 of the housing of the
linear mechanical actuator arrangement 204. The upper section 214,
of the housing of the linear mechanical actuator arrangement 204
includes sufficient head space to accommodate a portion of the
actuator rod 242 extending above the clamp 248. It will be
appreciated that, in some embodiments of the invention, a linear
rod pumping apparatus 200 may be formed without the actuator rod
242 such that the polished rod 52, or an extension thereof, may be
fed longitudinally entirely through the rack 206 and clamped above
the upper end 236 of the rack 206 with a clamp 248. It is
contemplated, however, that the addition of the actuator rod 242
will substantially facilitate installation of a linear rod pumping
apparatus according to the invention.
[0097] As shown in FIG. 9, some forms of the second exemplary
embodiment 200 of the invention may also include a tubular-shaped
spacer 249 disposed about the actuator 242 between the clamp 248
and the top plate 238 of the rack 206. Such a spacer 249 may be
utilized when practicing the invention with a clamp 248 having a
peripheral dimension which is larger than an opening 217 in the
center section 216 of the housing.
[0098] As shown in FIGS. 7, 8 and 10, the linear mechanical
actuator arrangement 204 of the second exemplary embodiment 200 of
the invention includes four guide rollers 250 arranged in two
pairs, attached to the center section 216 of the housing
substantially opposite the pinion 208, and configured to bear
against the longitudinally extending distal edges of the legs 226,
228 of the rack 206 for urging the rack 206 into a gear mesh
relationship with the pinion 208. Two guide bars 252, operatively
extending from the middle section 216 of the housing and
substantially opposite from one another, are provided for urging
the rack 206 into alignment with the pinion 208.
[0099] The middle section 216 of the housing functions as a pinion
housing, having a longitudinally extending opening 254 (see FIG.
10) disposed about the pumping axis 220 for passage therethrough of
the rack 206, and defining a rotational axis 256 of the pinion 208,
with the pinion axis 256 being laterally offset from, and extending
substantially perpendicularly to, the pumping axis 220.
[0100] A first, anti-drive end of the pinion 208 is journaled in a
pinion bearing 258 disposed in, and mounted to, the pinion housing
216. The second, drive end 260 of the pinion 208, in the linear
mechanical actuator 204 of the second exemplary embodiment 200, is
adapted for connection to an output element 262 of the gearbox 210
and is supported by an output bearing 264 of the gearbox 210. By
virtue of this arrangement, the output bearing 264 of the gearbox
210 serves two functions and provides a more compact assembly than
would be achievable in an embodiment of the invention having an
additional bearing attached to the middle housing 216 for
supporting the drive end 260 of the pinion 208. In other
embodiments of the invention, however, an additional bearing may be
provided for supporting the drive end 260 of the pinion 208.
[0101] To further reduce the size of the second exemplary
embodiment of the linear rod pumping apparatus 200, the gearbox 210
is a right angle gear box having input and output elements 266, 262
(see FIGS. 7 and 10) arranged substantially at a right angle to one
another, with the output element 262 being oriented for alignment
with, and rotation substantially about, the pinion axis 256, and
the input element 266 of the gearbox 210 and the rotatable shaft
222 of the motor 212 being oriented substantially parallel to the
pumping axis 220. It will be understood that, in other embodiments
of the invention, a motor 212 may be operatively attached to the
pinion 208 by a variety of other means and in other relative
orientations.
[0102] As best seen in FIG. 8, the linear mechanical actuator
arrangement 204, of the second exemplary embodiment 200 of the
invention, also includes an oil sump, formed by the lower section
218 of the housing, and configured for containing a sufficient
volume of lubricant therein, such that a lower portion of the rack
206 is immersed into the lubricant during at least a portion of
each stroke 84 of the pump 68 (FIG. 2). The sump includes inner and
outer longitudinally extending radially spaced tubular walls 270,
272 sealingly connected at lower ends thereof by the bottom end of
the lower section 218 of the housing, to thereby define an
annular-shaped cavity therebetween, for receipt within the cavity
of the volume of the lubricant, and terminating in an
annular-shaped opening between upper ends of the inner and outer
tubular walls 270, 272. As will be understood from an examination
of FIGS. 8 and 9, the inner tubular wall 270 of the sump 268 has an
inner periphery thereof disposed about the actuator rod 242, and an
outer periphery thereof disposed within the channel 230 in the rack
206. The outer tubular wall 272 of the sump 268 has an inner
periphery thereof disposed about the rack 206.
[0103] As shown in FIG. 8, the inner tubular wall 270 extends
substantially above a fluid level 274 of the lubricant within the
sump 268, even when the rack 206 is positioned in a maximum
downward location thereof, so that the lubricant is precluded from
flowing over the top end 275 of the inner tubular wall 270. By
virtue of this arrangement, it is not necessary, in the exemplary
embodiment 204 of the linear actuator arrangement of the second
exemplary embodiment 200 of the invention, to provide any sort of
packing between the lower end of the lower section 218 of the
housing and the polished rod 52, or the actuator rod 242. It will
be noted, however, that in other embodiments of the invention,
other arrangements for providing lubrication of the rack in a sump
may be utilized, wherein it would be desirable to provide a packing
between the rod 52, 242 and the lower end of the lower section 218
of the housing of the linear mechanical actuator arrangement
204.
[0104] With reference to FIG. 7, it is further contemplated that,
in some embodiments of the invention, it may be desirable to have
the cross-sectional area of the sump 268 match the cross-sectional
area of the rack 206, or a lower end plate 276 (see FIG. 8) closely
enough so that immersion of the rack into the sump 268 generates
hydraulic damping of the movement of the rack 206.
[0105] As shown in FIGS. 7 and 8, the linear mechanical actuator
arrangement, in the second exemplary embodiment of a linear pumping
apparatus 200 according to the invention, includes a pair of nested
helical compression springs 278, 280, operatively positioned within
the annular cavity in the bottom of the sump 268, below the lower
end 234 of the rack 206, and configured for engaging and applying
an upwardly directed force to the lower plate 276 on the lower end
234 of the rack 206, when the lower end plate 276 comes into
contact with a longitudinally movable spring contact plate 282
configured to rest on an upper end of the springs 278, 280 and move
longitudinally along the inner tubular wall 270 as the springs 278,
280 act on the lower end 234 of the rack 206.
[0106] In the exemplary embodiment 200, the springs 278, 280 are
configured for engaging and applying an upwardly directed force to
the lower end 236 of the rack 206 only when the lower end 234 of
the rack 206 has moved beyond a normal lower position of the rack
206 during a pump stroke. Such an arrangement provides a safety
cushion to safely bring the rack and rod string slowly to a halt in
the event that a fault condition should result in the rack 206
moving downward to a longitudinal position lower than would be
attained during a normal pump stroke. By virtue of this
arrangement, a potentially damaging impact between components of
the linear mechanical actuator arrangement and/or between the
stationary and traveling members of the pump 68 is precluded.
[0107] In other embodiments of the invention, however, the springs
278, 280 may be configured in such a manner that they engage and
apply an upwardly directed force to the lower end of the rack
during a portion of each pump stroke, to thereby recover a portion
of the kinetic energy generated by the weight of the rod string and
pump during the downward portion of the pump stroke under the force
of gravity and utilize that stored energy in the springs 278, 280
for aiding the action of the linear rod pumping apparatus during
the upward portion of the stroke, in addition to precluding
mechanical damage the rack 206 or other components at the bottom of
each pumping stroke.
[0108] As best seen in FIGS. 8 and 10, the second exemplary
embodiment of a linear rod pumping apparatus 200 also includes a
position sensing arrangement for sensing a position of the rack 206
along the pump axis 220. Specifically, the position sensing
arrangement of the second exemplary embodiment 200 includes a
stationary position sensor 284 disposed adjacent the rack 206 at a
mid-stroke position along the pumping axis 220 in combination with
upper and a lower sensor flags 286, 288 attached to the rack 206,
respectively, at the upper and lower ends 236, 234 of the rack 206.
The first and second sensor flags 286, 288 are positioned along the
first leg 244 of the rack 206 in such a manner that the flags 286,
288 are brought into juxtaposition with, and sensed by, the sensor
284 during each complete pumping stroke.
[0109] The upper sensor flag 286 and lower sensor flag 288 are
axially spaced from one another along the rack 286 to form a gap
between the upper and lower flags 286, 288 with the gap being
substantially centrally longitudinally disposed along the rack 206.
The upper sensor flag 286 extends substantially from the upper end
236 of the rack 206 to a lower edge 290 of the upper sensor flag
286, which defines an upper end of the gap between the upper and
lower sensor flags 286, 288. The lower sensor flag 288 extends
substantially from the lower end of the rack 206 to an upper edge
292 of the lower sensor flag 288, to thereby define the lower end
of the gap between the upper and lower sensor flags 286, 288.
[0110] By virtue of this arrangement, the sensor 284 produces an
output, as shown in FIG. 11, having a substantially square wave 294
shape, with a step change from a first state 296, while one or the
other of the flags 286, 288 is juxtapose with the sensor 284, to a
second state 298, when the gap is juxtapose with the sensor
284.
[0111] The sensing arrangement described above, in relation to the
second exemplary embodiment 200 of the invention, can be used with
great efficacy in combination with control apparatuses and methods
of the type described in commonly assigned U.S. Pat. No. 7,168,924
B2, to provide a highly precise, accurate, effective and efficient
calculation of the polished rod position and control of the linear
rod pumping apparatus 200. The exemplary embodiment of the sensing
arrangement described above can also be utilized to control the
motor 212 in such a manner that downward motion of the rack 206 is
slowed as the bottom of the pump stroke is approached through
braking action of the motor 212, to thereby provide an electrically
controlled velocity profile, which may be used in addition to, or
in place of, the springs 278, 280 of the second exemplary
embodiment of a linear rod pumping apparatus 200.
[0112] FIG. 12 shows a third exemplary embodiment of a linear rod
pumping apparatus, according to the invention, having a linear
mechanical actuator apparatus 302, including a rack 304 and pinion
306 gear train arrangement, similar to the rack and pinion
arrangement of the second exemplary embodiment 200 described above.
The linear mechanical actuator 302, of the third exemplary
embodiment 300, as shown in FIG. 11, is mounted directly to the
well head 54, through a standoff arrangement 308.
[0113] The third exemplary embodiment of a linear rod pumping
apparatus 300, according to the invention, is similar in many
respects to the second exemplary embodiment 200, described above,
with several exceptions. In the third exemplary embodiment 300, the
polished rod 52 is shown as extending completely through the rack
304 along the pumping axis 220, and is secured at both the upper
and lower ends of the rack 304 by upper and lower end plate and
clamp arrangements 310, 312. A stop block 314 is fixedly attached
to the middle section 316 of the housing, in such a manner that the
end plate and clamping arrangements 310, 312 will contact the stop
block 314, and arrest further movement of the rack 304, to preclude
having the rack 304 run off of the pinion 306.
[0114] The third exemplary embodiment of the linear pumping rod
apparatus 300 also includes only a single pair of guide rollers
318, disposed for urging the rack 304 into a gear mesh arrangement
with the pinion 306.
[0115] In the form illustrated in FIG. 12, the linear mechanical
actuator arrangement 302 of the third exemplary embodiment of the
linear rod pumping apparatus 300 further, does not include the oil
sump 268 or the springs 278, 280 of the second exemplary
embodiment. It will be understood, however, that in alternate
embodiments of the invention, various features of the exemplary
embodiment shown herein can be used, omitted, or combined together
in forms other than the exemplary embodiments of the invention
shown in the drawings and specifically described herein.
[0116] FIG. 13 shows a fourth exemplary embodiment of a linear rod
pumping apparatus 400, according to the invention, in which a
linear mechanical actuator arrangement 402 that is substantially
identical to the linear mechanical actuator arrangement 302 of the
third exemplary embodiment 300 of the invention described above,
includes a piston plate 404 attached to the lower end of the rack
406 of the rack 406 and pinion 408 arrangement, and the lower end
of the lower section 410 of the housing is cooperatively configured
with the piston plate 404 in such a manner that a gas tight
cylinder is provided, below the piston plate 404. A pneumatic
storage apparatus 414, such as an accumulator, is connected to the
pneumatic cylinder chamber 412 through a conduit 416, and a
regulator 418 is disposed between the accumulator 414 and the
cylinder 412 for regulating pressure and volume of the gas stored
in the pneumatic cylinder and accumulator 412, 414.
[0117] By virtue of this arrangement, a counter-balance force may
be applied to the lower end of the rack 406. Although only a
singular accumulator 414 and regulating valve 418 are illustrated
in FIG. 12, in some embodiments of the invention it may be
desirable to have multiple accumulators and/or regulating valves
414, 416, to aid in adjusting the counter-balance force applied to
the lower end of the rack. Some embodiments of the invention may
also include venting part, or all of the pressure generated in the
pneumatic cylinder cavity 412 on the downstroke. In the exemplary
embodiment shown in FIG. 13, the interior of the lower section 410
of the housing is vented to atmosphere above the highest level of
travel of the piston plate 404.
[0118] It will be understood, that the pneumatic counter-balancing
arrangement of the fourth exemplary embodiment 400 of the invention
may also be incorporated into other embodiments of the invention,
including some or all of the features of the first and second
exemplary embodiments 100, 200 of the invention described
above.
[0119] FIG. 14 shows a first exemplary embodiment of a motor drive
500 for use in a control arrangement in embodiments of the
invention having an electric motor. The motor drive 500 includes a
rectifier bus charging section 502, a capacitor bank section 504, a
dynamic braking section 506, and an inverter motor output section
508 connected along common bus rails 510, 512, for connecting a
three phase power input R, S, T to a three phase output U, V, W,
provided to the motor.
[0120] When the motor is drawing power, diodes in the charging
section 502 charge the capacitor bank 504 and an IGBT bridge
arrangement in the inverter motor output section 508 modulates
capacitor voltage to control current in the motor windings.
[0121] When the motor is regenerating power, due to braking action,
as the rod string pulls the rack downward on the return/fill
portion of the pump stroke, for example, diodes in the inverter
motor output section 508 transfer power to the capacitor bank 504,
causing capacitor bank voltage to rise. The first exemplary
embodiment of the motor drive 500 provides two options for dealing
with the energy that is transferred to the capacitor bank during
braking. In some forms of the invention, the capacitor bank 504
includes sufficient capacitance to store the energy generated
during braking action, without exceeding voltage limits on the
rails 510, 512. Alternatively, a dynamic braking IGBT 514 in the
dynamic braking section 506 may be turned on to allow the energy
generated during braking action to be dissipated across a dynamic
braking resistor 516 of the dynamic braking section 506.
[0122] FIG. 15 shows a second exemplary embodiment of a motor drive
600 for use with an electric motor in practicing the invention. The
second exemplary embodiment of the motor drive 600 is substantially
identical to the first exemplary embodiment of the motor drive 500,
as described above, except that an IGBT switching bridge is
provided in parallel with the diodes in the rectifier section to
provide a regenerative bus charging section 602, a capacitor bank
section 604, a dynamic braking section 606 and an inverter motor
output section 608 disposed across a pair of common rails 610, 612
for connecting a three phase R, S, T input to the motor drive to a
three phase U, V, W connection to the motor.
[0123] In the second exemplary embodiment of the motor drive 600,
when the motor is drawing power the diodes in the regenerative bus
charging section 602 charge capacitors in the capacitor bank 604
and an IGBT bridge in the inverter motor output section 608
modulates capacitor voltage in the capacitor bank section 604 to
control current in the motor windings.
[0124] In the second exemplary embodiment of the motor drive 600,
when the motor regenerates power due to braking action, diodes in
the inverter motor output section transfer power to the capacitor
bank 604, causing capacitor bank voltage to rise. The second
exemplary embodiment of the motor drive 600 provides three options
for dealing with the energy being transferred to the capacitor
bank.
[0125] In one option, the capacitor bank section 604 has sufficient
capacitance to store the energy generated during braking, without
exceeding voltage limits.
[0126] With the second option, a dynamic braking IGBT 614 of the
dynamic braking section 606 is turned on, and all, or a portion of
the energy generated during braking, is dissipated across a dynamic
braking resistor 616 of the dynamic braking section 606.
[0127] In the third optional mode of operation, the IGBTs in the
regenerative bus charging section are switched to modulate the
capacitor voltage of the capacitor bank section in such a manner as
to allow a transfer of the power generated during braking back to
the incoming three phase R, S, T source.
[0128] FIGS. 16 and 17 show a fifth exemplary embodiment of a
linear rod pumping apparatus 700, according to the invention, in
which a linear mechanical actuator arrangement 702 that is
substantially identical to any of the first, second, third or
fourth linear mechanical actuator arrangements except the polished
rod 52 does not pass through the body of the rack 716 nor does
polished rod 52 clamp to the rack 716. This embodiment includes a
pulley support frame 714 attached to the base plate 718 of the
arrangement supporting two pulleys 706 at a point above the
uppermost extension of the rack 716. Two cable clamps 708 attach
two cables 704 to the upper plate of the rack 716. The cables pass
over the pulleys 706 and are attached to a rod clamping arrangement
712 by means of two cable clamps 710. The rod clamping arrangement
712 is clamped to the polished rod 52 of the pumping system.
[0129] By virtue of this arrangement, a downward force on the rack
716 results in an upward force on the polished rod 52. This
arrangement will preserve a more correct alignment of the rack 716
in some cases.
[0130] It will be understood, that the pneumatic counter-balancing
arrangement of the fourth exemplary embodiment 400 of the invention
may also be incorporated into this embodiments of the invention.
However, the piston would be arranged to provide a downward force
on the rack 716. Also, the spring arrangements of other embodiments
would be moved to the top of the rack travel in this
embodiment.
[0131] FIGS. 18 and 19 show a sixth exemplary embodiment of a
linear rod pumping apparatus 800, according to the invention, in
which a linear mechanical actuator arrangement 802 that is
substantially identical to any of the first, second, third or
fourth linear mechanical actuator arrangements except the polished
rod 52 does not pass through the body of the rack 816 nor does
polished rod 52 clamp to the rack 816. This embodiment includes a
pulley support frame 814 which is attached to the top plate of the
rack 816 and supports two pulleys 806 such that the movement of the
rack 816 causes the pulleys 806 to be raised and lowered. Two cable
clamps 808 attach two cables 804 to the base plate 818 of the
arrangement. The cables pass over the pulleys 806 and are attached
to a rod clamping arrangement 812 by means of two cable clamps 810.
The rod clamping arrangement 812 is clamped to the polished rod 52
of the pumping system.
[0132] By virtue of this arrangement, movement of any given
distance of the rack 816 results in a movement of twice the given
distance by the polished rod 52. This arrangement is beneficial
where a longer stroke length is desired, but overall height of the
mechanism must be limited.
[0133] Those having skill in the art will recognize that, through
practice of the invention, significant advantages are provided as
compared to prior pumping apparatuses and methods, such as the
control of a walking-beam-type, or a belt-driven, pumping apparatus
controlled by a rod pump control system as disclosed in the
above-referenced, commonly assigned, U.S. Pat. No. 7,168,924 B2, to
Beck et al., titled "Rod Pump Control System Including Parameter
Estimator." It will be further recognized that a rod pump control
system, including parameter estimation, of the type disclosed in
Beck et al., U.S. Pat. No. 7,168,924 B2, may be used with
considerable efficacy in combination with a linear rod pumping
apparatus, according to the present invention, with the disclosure
and teachings of Beck et al. being incorporated herein, in their
entireties, by reference.
[0134] For example, it will be readily appreciated that in a linear
rod pumping apparatus, according to the invention, the surface
position of the pump rod, and the current load on the pump rod
above the surface of the ground may be readily determined, without
the need for down-hole sensors, by virtue of the elegantly simple
construction of the linear mechanical actuator arrangement and the
direct relationship that exists between the vertical position of
the vertically movably member of the linear mechanical actuator
arrangement and the rotatable element of the motor. Where the motor
is an electric motor, for example, the vertical position of the
vertically movable member can be directly determined from the
angular rotational position of the motor shaft, and the load on the
rod above the surface of the ground can be readily determined from
motor current and voltage, in accordance with the apparatuses and
methods of a rod pump control system including parameter
estimation, as taught by Beck et al., or through the use of other
applicable methods and apparatuses in accordance with the teachings
with the present invention. Other parameters useful for controlling
a linear rod pumping apparatus, in accordance with the invention,
such as direction and speed of the vertical member and/or the motor
shaft, and the magnitude and direction of motor torque can also
readily be obtained through use of a rod pump control system
according to Beck et al., or any other appropriate apparatus and
method in accordance with the presence invention.
[0135] Once the above-ground parameters, such as surface rod
position and load are determined for a linear rod pumping
apparatus, according to the invention, a model of dynamic rod
performance, of the type disclosed in Beck et al., or any other
appropriate apparatus or method for modeling the dynamic
performance of the pump rod, may be utilized to determine a
down-hole pump position and load. The pump dynamic model may then
also be utilized to determine pump "fillage" as a percentage of the
total capacity of the sucker-rod pump, in real time.
[0136] Operation of the linear rod pumping apparatus can then be
controlled and adjusted to provide a vertical stroke length and
speed of the vertically movable member of the linear rod pumping
apparatus, according to the invention, to achieve a target desired
pump fillage percentage. Practice of the invention also
contemplates controlling the linear rod pumping apparatus in a
manner consistent with optimizing other performance parameters of a
particular well installation, such as minimizing power consumption
by the motor for a given volume of pumped fluid, or minimizing
variation in the level of input power draw in a manner which might
be desirable in hydrocarbon well installations wherein the motor of
the linear rod pumping apparatus receives input power from an
engine-driven generator.
[0137] Those having skill in the art will readily recognize that
the elegantly simple construction of a linear rod pumping
apparatus, according to the invention, results in the operating
members having very low inertias, as compared to prior pumping
apparatuses.
[0138] Those having skill in the art will further recognize that
the elegant simplicity of construction and operation of a linear
rod pumping apparatus, according to the invention, is inherently
much more readily controllable than walking-beam-type apparatuses
in which complex kinematic motions and large inertias of multiple
interconnected parts must be taken into consideration, in the
manner disclosed, for example, in the Beck et al. U.S. Pat. No.
7,168,924 B2, in order to determine the present position and
loading on the pumping apparatus and control the input being
provided by the pumping apparatus to the pump rod. The
complexities, and in particular the high inertias, of prior pumping
apparatuses also make it difficult to efficiently and effectively
provide control inputs for modifying performance of the down-hole
pump in real time.
[0139] The low inertia of a linear rod pumping apparatus, according
to the invention, provides particular advantages in affecting real
time control of the pumping apparatus, in a manner consistent with
achieving a desired performance from the sucker-rod pump. In some
modes of operation, however, the low inertia of a linear rod
pumping apparatus, according to the invention, must be taken into
account and compensated for, to preclude having the weight of the
rod string and fluid load accelerate the vertically movable member
of the linear rod pump downward more rapidly than is desirable
during the downward portion of the pump stroke under conditions
such as a loss of power to the motor, for example, or periods of
operation in which the traveling valve of the sucker-rod pump is
not immersed in fluid having sufficient viscosity to provide
hydraulic damping of the downward movement of the traveling valve
and rod string. Under such operating conditions, the controlled
stop provisions at the bottom of the motion of the apparatus, as
described above, as provided mechanically through spring elements,
or electrically through braking of the motor are provided by the
present invention, for use in combination with a rod pump control
system such as the one described in Beck et al., or another
appropriate control system to preclude having the rod string drive
the vertically movable member of a linear rod pumping apparatus,
according to the invention, at an undesirably high speed and/or
acceleration rate, and to preclude damaging of the down-hole pump
components by preventing "tagging" of the standing valve by the
traveling valve.
[0140] With specific reference to the second exemplary embodiment
of a linear pumping rod apparatus 200, according to the invention,
as described above, a method of operating a linear rod pumping
apparatus, according to the invention, might include the following
eight steps. During all eight steps, the instantaneous vertical
velocity of the rack 206 is calculated from the instantaneous
angular velocity of the motor shaft 222, and the position of the
actuator rod 242 is calculated by integration using the
instantaneous vertical velocity of the actuator rod 242.
[0141] Step 1. Begin with the actuator rod 242, in a fully lowered
position, and attached to the upper end of the polished rod 52
[0142] Step 2. The motor 212 is then energized to accelerate the
rod to a predetermined "UP SPEED."
[0143] Step 3. As the motor 212 drives the rack 206 upward, to
thereby accelerate the actuator rod 242 to UP SPEED, the output
signal 294 (see FIG. 10) of the stationary position sensor 284 is
monitored to detect the rising edge of the square-wave 294 caused
by the upper edge 292 of the lower reference flag 288 coming into
juxtaposition with the position sensor 284.
[0144] If the upper edge 292 is detected before the rod 242 reaches
a calculated vertical rod position, corresponding to a desired pump
stroke, where the upper edge 292 is within a predetermined
reference position window, or where the upper edge 292 is not
detected within a predetermined period of time or a predetermined
angular rotation of the motor shaft 222, a fault condition is
identified and the motor 212 is operated in such a manner that the
rack 206 and actuator rod 242 are lowered to the fully lowered
position at a very slow speed. Once the fully lowered position is
achieved, the method may begin again by returning to step 1.
[0145] If the upper edge 292 of the lower reference flag 288 is
detected, however, while the calculated rod position is within the
predetermined raised rod reference position window, the calculated
rod position is set to the raised rod reference position value, and
the instantaneous vertical position of the actuator rod 242 is
calculated by integration using the upward velocity of the actuator
rod 242.
[0146] Step 4. As the actuator rod 242 approaches a desired top of
stroke position, the motor 212 is operated in such a manner that
the upward speed of the rod 242 decelerates so that the upward
velocity is reduced to substantially zero at the desired top of
stroke position.
[0147] Step 5. From the top of stroke position, the motor 212 is
operated in such a manner that the actuator rod 242 accelerates to
a "DOWN SLOW SPEED." From the foregoing description of exemplary
embodiments, it will be understood that during downward motion of
the actuator rod 242, the motor 212 is operated in a braking mode,
by commanding the motor 212 to drive the pinion 208 at a slower
rotational speed than the pinion 208 would otherwise achieve due to
the downward forces on the rack 206 caused by the weight of the rod
string and any fluid loads acting on the sucker-pump apparatus, so
that a net braking torque is applied to the pinion 208.
[0148] Step 6. As the rod 242 moves downward, at DOWN SLOW SPEED,
the output of the position sensor 282 is monitored to detect a
rising edge of the reference signal 294 caused by the lower end 290
of the upper reference flag 286 coming into juxtaposition with the
position sensor 282. If this edge 290 is detected before a
predetermined calculated rod position whereat the rod 242 is within
a lowered rod reference position window, or is not detected, a
fault condition is identified and the motor 212 is operated in such
a manner that the actuator rod 242 is lowered to the fully lowered
position at a very low speed. Once the actuator rod 242 has reached
the fully lowered position, the method may then return to step 1
above. If, however, the lower edge 290 of the upper reference flag
286 is detected, while the calculated rod position is within a
desired lower rod reference position window, the calculated rod
position is reset to the measured lowered rod reference position
value, and the rod 242 is allowed to continue downward, while rod
position is calculated by integration of the downward velocity of
the rod 242.
[0149] As the actuator rod 242 is lowered, load on the down-hole
pump is determined, by monitoring motor torque, for example. When
the load on the down-hole pump drops to a very low level, i.e.
drops below a predetermined threshold indicating that the traveling
valve has opened, the motor 212 is operated such that the actuator
rod 242 can accelerate to a "DOWN FAST SPEED."
[0150] Step 7. As the actuator rod 242 continues downward at DOWN
FAST SPEED, the vertical position of the actuator rod 242 is
monitored, and the down-hole position of the traveling valve is
calculated. As the actuator rod 242 approaches a predetermined
bottom of stroke position, which may be vertically above the fully
lowered position of the actuator rod 242, the motor 212 is operated
in a braking mode, to provide a velocity profile, such that the
actuator rod 242 is decelerated to substantially zero velocity at
the desired bottom of stroke position.
[0151] Step 8. Once the actuator rod 242 has reached the desired
bottom of stroke position, operation of the linear rod pumping
apparatus 200 is continued by returning to step 2 above, and
repeating steps 2-8 for each pump stroke.
[0152] With reference to FIGS. 2 and 13, operation, according to
the invention, of a linear pumping apparatus having an electric
motor driven by a motor drive 110, 500 controlled by a controller
108 will be described, for a "power loss" fault condition, wherein
the method may include the following four steps:
[0153] Step A. The controller 108 detects a loss of line power
whenever voltage across the common power busses 510, 512 drops
below a predetermined minimum threshold value.
[0154] Step B. If the actuator rod 242 is moving upward, at the
time that a line power loss is detected, the controller 108
commands the motor 104, 212 to enter a reverse braking mode in
which the motor 104, 212 acts as a generator as the rack 206
continues to move upward, due to inertia in the linear rod pumping
apparatus, to keep the voltage across the busses 510, 512 at a
level which would allow the motor drive 110, 500 to continue to
control the motor 104, 212.
[0155] Step C. If the actuator rod 242 is moving downward, at the
time that a line power loss is detected or after braking action of
Step B has caused the actuator rod 242 to begin downward motion,
the controller 108 commands the motor 212 to operate in a braking
mode, to limit the lowering speed of the actuator rod 242 in such a
manner that impact forces are reduced when the rack 206 contacts
the springs 278, 280, and also causing the motor 104, 212 to act as
a generator and keep the voltage across the busses 310, 312 at a
level which allows the motor drive 110, 500 to continue to control
the motor 104, 212.
[0156] Step D. When the actuator rod 242 has reached a fully
lowered position, the voltage across the busses 310, 312 will decay
and the motor drive 110, 500 is turned off until line power is
restored.
[0157] Those having skill in the art will recognize, that the
above-described exemplary embodiments of normal operation and
various fault conditions, for exemplary embodiments of the
invention, are provided solely for the purpose of helping the
reader to more fully understand the invention, and are by no means
intended to limit the scope of the invention. It will be further
understood, that the invention may be practiced in a wide array of
other forms, within the scope of the invention.
[0158] Those having skill in the art will also appreciate, that a
linear rod pump apparatus and/or method, according to the
invention, provides significant advantages, in addition to being
physically smaller, in comparison to both a conventional walking
beam pumping apparatus, and other prior pumping apparatuses, such
as the hydraulic motor driven pump jack device of Saruwatari.
[0159] All references, including publications, patent applications,
and patents cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0160] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) is to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0161] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *